This invention relates to noise suppressing apparatus and, more specifically, a combination noise suppressor and baffle for suppressing fan noise generated in the cooling system of power units including liquid-cooled engines.
Prior art of possible relevance includes the following U.S. Pat. Nos. 3,812,927 issued May. 28, 1974 to Kawamura; and 3,857,453 issued Dec. 31, 1974 to Buttke et al.
A considerable percentage of the noise generated during the operation of a power unit including a liquid-cooled, internal combustion engine, is generated by the fan typically employed to drive air through a radiator for the engine coolant. With present day concern for the lowering of noise levels attendant the operation of any type of machinery, there has been increasing focus on minimizing the noise generated by fans utilized in the cooling system of power units including a liquid-cooled engine. In many cases, fan designs have been made more efficient so as to either minimize the size of the fan required to produce a given air flow or minimize its operating speed, thereby decreasing the amount of noise generated by reason of the resulting ability to utilize a smaller or slower fan. In taking such an approach, a point is reached whereat only marginal improvement can be attained since as long as a fan is required, there will be noise attendant to its operation.
In other cases, in systems where air is forced through a radiator by a fan, it has been suggested to place a noise absorber in the path of the air exiting the fan. Care must be taken, however, to ensure that the noise absorber does not impede the flow of air through the radiator by creating a backpressure, for such would reduce the cooling capability of the system; and if too severely reduced, would require the use of a larger or higher speed fan with the resulting consequence of an increase in the noise level due to the use of a larger fan or higher speed. Also, the more conventional absorbers are subject to damage during vehicle operation.